In recent years, an optical module used in network equipment is becoming more multichannel, higher in speed and smaller in size. One example of the optical module adapted to become more multichannel, higher in speed and smaller in size is an optical module including the optical element including a photo detector and a light emitter and a light emitting element formed on a circuit substrate, a lens block having a lens facing to the optical element, and a ferrule connected to the lens block, the ferrule in which an optical fiber is inserted (see Patent Document 1).
Patent Document 1: JP-A-2010-122312
When the inside of the optical module is provided with a photoelectric conversion part for converting an electrical signal into an optical signal, it is necessary to design the whole module in consideration of heat generated in the photoelectric conversion part. On the other hand, workability of an assembly process of assembling the module is also one important problem.
In the optical module disclosed in Patent Document 1, the lens block is mounted in the end of the circuit substrate and a protrusion formed on the ferrule is inserted into a hole bored in the lens block to thereby connect both members. However, since this configuration does not have a region in which the ferrule is mounted on the circuit substrate, insertion work of the ferrule cannot be done along the circuit substrate and workability decreases. Also, when an assembly worker accidentally applies a force vertical to a connection direction to the ferrule after connection between both members, the protrusion formed on the ferrule may break.
Hence, in the optical module of Patent Document 1, it is contemplated to extend the end of the circuit substrate to a predetermined region in which the ferrule is mounted and support the ferrule by a part of the circuit substrate. However, in this configuration, heat generated in the photoelectric conversion part concentrates on the lens block or the ferrule. Then, since the lens block differs from the ferrule in a thermal expansion coefficient, different thermal stresses are applied to the lens block and the ferrule. When the different thermal stresses are applied to the portion of bonding between the lens block and the ferrule, unexpected variations are given to the portion of optical coupling between the lens block and the ferrule, and communication quality may deteriorate.
An object of the invention is to provide an optical module capable of reducing an influence of heat generated in a photoelectric conversion part while ensuring workability at the time of assembly.